A liquid crystal display (LCD) panel in a thin-film transistor liquid crystal display (TFT-LCD) has the advantages of good brightness, high contrast, low power consumption, small size, light weight, etc. Meanwhile, the LCD panel has the advantages of mass production, high automation degree, low cost of raw materials and wide development space, and is a hotspot in global economic growth in the 21st century.
The LCD panel comprises an active display area and a peripheral circuit area. A plurality of pixels are disposed in the active display area to form a pixel array. A peripheral circuit is disposed in the peripheral circuit area. For instance, each pixel includes a thin-film transistor (TFT) and a pixel electrode connected with the TFT. For instance, each pixel is encircled by two adjacent scanning lines and two adjacent data lines. Generally, the scanning lines and the data lines extend from the active display area to the peripheral circuit area and are electrically connected with a driver chip through the peripheral circuit. In general, the driver chip has specified size design, and the peripheral circuit is connected with one end of the scanning line and one end of the data line with an area provided with the driver chip to form a fan-out area.
With the development of display technology, display products need to adopt a narrow-bezel design to achieve perfect visual effect, so the line width and the line spacing must be reduced. However, as the conventional wiring design has reached a resolution limit of an exposure machine, if the line width and the line spacing are further reduced, the risk of breakage and short circuit of lines can be caused in the manufacturing process.
Moreover, it has been found that by using a same pattern on a mask during a manufacturing process, lines formed in a pixel area after photolithography are thinner than lines formed in a fan-out area after photolithography. The reasons are as follows: (1) in the aspect of layout, the lines in the pixel area are relatively sparse while the lines in the fan-out area are relatively dense. Taking positive photoresist as an example, in the process of forming lines, photoresist among the lines are subjected to exposure and removed by development. Thus, in the process of development, as the lines in the fan-out area are dense, the photoresist among the lines is difficult to remove, so the lines in the fan-out area are relatively wide. (2) In the aspect of luminous intensity distribution, the lines in the fan-out area are dense. Taking positive photoresist as an example, transmissive regions on a mask correspond to gaps between the lines. When light is irradiated to the mask, the transmissive regions of the mask are equivalent to slits and constitute a transmissive diffraction grating. When the wiring is denser and the number of the slits is larger, the grating constant is smaller, and bright fringes formed by grating diffraction are brighter and thinner. Therefore, the size of an exposure area is reduced, and hence the width of the lines in the fan-out area is increased. (3) In the aspect of imaging, the exposure machine is actually an imaging optical system. Each imaging system has cut-off frequency, and the system cannot run through an object (an image on the mask) spectrum higher than the cut-off frequency. As for the image on the mask, when the lines are denser and the number of high-frequency components is larger, more information will be cut-off in the process of imaging, and hence the difference between the exposed area of the photoresist and the image on the mask can be larger.
Therefore, how to achieve the narrowing of the lines in the fan-out area is the technical problem to be solved in the art in view of the phenomena that: the resolution of the current exposure machine has reached limit and there is bottleneck in the manufacturing process of fan-out areas of narrow-bezel and high-PPI products.